The present invention relates to an electrical control unit for an automobile. Especially, the present invention relates to an electrical control unit for an automobile started by a wake-up signal other than the ignition switch signal, even when the ignition switch is cut off.
Microcomputer is indicated when the wake-up starting circuit generates the wake-up trigger signal by inputting external switch, and this signal is input to the interrupt terminal of microcomputer and the composition that wake-up is done is disclosed in Japanese Patent Application Laid-Open No. 2002-108519.
The conventional electrical control unit needs to keep supplying the electric current from the battery when the ignition switch is cut off, because it cannot start according to a wake-up signal other than an ignition switch signal.
However, when the electric current consumption at this sleep, that is, the standby electric current is large, the amount of the electrical discharge from the battery increases when the automobile is not driven for a long term. As a result, the possibility that the engine cannot be started may occur. It is required to decrease the standby electric current of an individual electrical control unit as much as possible because various equipment such as a lot of electrical control units are installed in the present automobile.
In the conventional wake-up method in which the wake-up signal is input to an interrupt terminal of the microcomputer, it is required to keep supplying the standby electric current to a CPU core of the microcomputer at the sleep. The standby electric current of the microcomputer is small in the conventional electrical control unit of the body system in which the circuit scale of the microcomputer is comparatively small. However, the microcomputer with high performance and multi-function is installed in the electrical control unit which controls the powertrain such as an engine, etc. Therefore, the leakage current is larger because the logic scale is larger than that of the microcomputer for the body system control. As a result, there is a problem that the standby electric current of the microcomputer, and thus the standby electric current of the electrical control unit increases. Further, because it is necessary to operate the same power supply circuit as the power supply circuit which supplies the electric current to the CPU core at the normal operation in order to supply the standby electric current to the CPU core, the standby electric current will be become larger.
For instance, the special description on how to wake up the electrical control unit cannot be found in U.S. Pat. No. 5,894,832.
Further, it is required to keep supplying the electric current to the electrical control unit for which the regular wake-up is necessary, when the ignition switch is cut off. In such a case, the wake-up method by which the wake-up signal is input to the interrupt terminal of the microcomputer is undesirable as described above. Further, the consumption current of the timer module installed in the microcomputer has the tendency that increases by the influence such as the leak to the modules in the surrounding, and it relates to the increase in the standby electric current, although the method by which the wake-up signal is output by using the timer module installed in the microcomputer is thought.